Alloy



Feb.2,1932. S OTT- 1,843,903

ALLOY Filed Aug. 11, 1927 4 Ur 1'lf Expansion I60 6 lbo 2'00 50 4'00 Degrees C enwiar-ade INVENTOR Howqrd Scott w ATTbRNEY Patented Feb, 2, 1 932 umrao er-Ares r aranr OFFICE HOWARD SCOTT, OF WILKINSBURG', PENNSYLVANIA, ASSIGNOR T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, .32. CORPORATION OF PENNSYLVANIA.

ALLOY Application filed. Ali gust 11, 1927. Serial No. 212,202,-

My invention relates to alloys and more particularly to alloys having a highcoeflicient of expansion;

An object of the invention is to provide a metallic alloy having a high coefficient of expansion that is uniform over a wide range of temperatures, the'alloy being also adapted to preserve its strength at high temperatures.

Another object of the invention is to provide a metallic alloy, the chief constituents of which are iron, manganese and nickel, that possesses a high coeflicient of expansion up to a temperature of 600 0., which makes it particularly useful as an element of a composite bimetallic article made up of two metals of relatively-different Coeificients of expansion.

A, further object of the inventionis to provide an alloy which shall have a high coefficient-of expansion that is almost linear, and which will, therefore, find special application in thermostatsrequiring high linear expansion over a wide range of temperature.

In the single figure ,of the accompanying drawing, the curves show a comparison of. one

of the improved nickel-iron-manganese alloys containing, inthis instance, .10 per cent nickel and 10 per cent manganese, with brass, Monel metal and 23 per cent manganese steel. Theordinates of the curve chart represent unit expansion in thousandths, and the abscissae represents degrees Centigrade.

Brass and Monel metal have commonly been employed for purposes which demand high thermal expansivity. Brass, however,

cannot be employed much above normal temperatures, because of its rapid loss of elastic strength with increasing temperatures,

which results in permanent deformation.- 40 While the elastic strength of Monel metal is higher than brass, it is still too low for Monel metal to be desirable as an element in a high-temperature bimetal member. Cold rolling partially overcomes this defect, but

-16 heating cold rolled metals causes a permanent I have found that an alloy composed essen-- 4 tially'of iron, nickel and manganese, mixed in such proportions that two and one-half times the amount of manganese plus the amount of nickel in the alloy will not be less than 30 or more than38 per cent, is easily workable, has a high coeficient of expansion over a wide range of temperatures, and if the manganese and nickel are added in substantially equal proportions, the coefiicient of expansion willbe substantially linear.

The qualities required in high expansion metal for alloys are (1) high coeflicient of.

expansion throughout the working range, (2) a suflicientelastic strength so that it will not suffer permanent deformation at any re quired temperature and (3) permanence of its elastic properties. It has been difficult to find a metal or alloy that has all of these characteristics, as metals of high elastic strength are characterized by low expansivity. Pure iron is no exception to this rule, for, if heat- I ed gradually, it will be found that iron has a low coeflicient of expansion that is almost uniform up .to about 900 degrees centigrade, but at this temperature the metal undergoes a change in crystalline structure known as a transformation point of the iron. Up to 900 degrees centigrade, the crystalllne struc ,ture of iron is known as alpha iron. From 900 to 1400 degrees C. pure iron expands uniformly but at a much higher rate than 1t does at temperatures below 900 degrees C. The

increased coefiicient of expansion between the temperatures of 900 and 1400 degrees centigrade is the property of a new crystalline structure known as gamma iron or austenite. The coeflicient of expansion of alpha iron is to X 10' centimeters per centimeter for each degree centigrade, whereas the coefiicient of expansion of gamma iron in either the iron-nickel or iron-manganese system of alloys. An iron base alloy with a high nickel content and without manganese has a high coefficient of expansion, but this property is not useful because of an irreversible transformation occurring near 1 ordinary temperatures. When the nickel content is sufiiciently high to suppress the irreversible transformation, a low coeficient of ex ansion, similar to that obtained in the well-Enown alloy invar, occurs at and above ordinary temperatures. The same phenomenon of lowexpansivity at and near normal temperatures occurs in high manganese-iron alloys, which have the additional undesirable feature of being workable only with difficulty. However, if manganese and nickel are added to iron in proportions such that the nickel content plus two and one-half times the manganese content are about 32 per cent, the irreversible transformation will not appear and a high coefiicient of expans1on may be obtained at a temperature ranging from -100 C. to 600 centigrade.

The alloy may be produced by the ordinary well known metallurgical processes, such as by melting iron, nickel and man ganese together, and it may also contain small percentages of impurities, although carbon should not be present in amounts greater than 0.3 per cent. When a greater amount of carbon than .3 of a per cent is added, however, the; expansion characterlstics become irreversible. It is, therefore, essential that the amount of carbon should not exceed .3 per cent- The characteristics of my improved alloy will be more readily understood by referring to the single figure of the drawing, in which brass is represented by curve 5, my manganese-nickel-iron alloy, composed in this instance of 10 per cent manganese and 10 per cent nickel, by curve 6, Monel metal by curve 7, and 23 per cent manganese steel by curve 8. It will be seen from the drawing that while the manganese-nickel-iron alloy does not have quite .as high a coefficient of expansion as brass or Monel metal at low temperatures, its coeflicient of expansion rapidly increases to the useful high expansion range as the temperature increases. At low temperatures, its

. rate of expansion is higher and considerably Expansion coeflicz'ents at low and high temperatures of high empansion alloys Coemcient of expansion (unit expansion per C. X 1G-) Temperature egmes 10% Mn Centigrade Monel Brass 10% N1 23% Mn steel steel 100 15. 4 21.0 19. 5 14. 5 100 150 16. 7 21.4 20. 2 17.5 200 16.0 21. 9 20. 8 19. 4. 250 16. 4 22. 3 21. 5 20. 6 300 16. 7 22. 6 22. 2 21. 6 350 17. 0 Sottens 22. 8 22. 6 400 Soltens 23. 5 2'3. 6 450 24. 2 21. 5 500 24. 8 25. 5

It is to be clearly understood that while curve 5, and the tables, show the coefficient of I expansion of an iron alloy containing 10% manganese and 10% nickel, these proportions 1 may be varied and a satisfactory alloy produced when nickel is present in amounts ranging from 1 to 34 per cent, and the manganese in amounts ranging from 12 to 1 per cent, it only being necessary that the manganese and nickel be added in such proportions that two and one half times the manganese, plus the nickel, will not be less than 30, nor more than 36 per cent.

It is recognized that'the coefi'icient of ex- 12a pansion of alloys vary in accordance with the impurities present and the proportion of the ingredients. In comparing my improved alloy with Monel metal,.brass and 23% manganese steel, it will therefore be understood that the impurities and ingredients of these alloys are present in such proportions that they will have the coefficient of expansion specified in the above table.

Various modifications may be made in practieing my invention without departing from" the spirit and scope thereof. I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. An alloy containing not more than .3% carbon and comprising about 80% of iron, about 10% of nickel and about 10% of manganese, said alloy having a coeflicient of expansion approximately equal to that of brass.

2. An alloy having a high reversible temperature coeificient of expansion comprising 5 to 30 a nickel, manganese in amounts ranging from 12 to 2% in accordance with the amount of nickel present and the remainder iron and minor impurities, said alloy containing not more than 3% carbon and the amount of nickel plus two and one-half times the manganese being not less than 30% nor more than 36% of the alloy.

3, An alloy havinga high reversible temperature coefficient of expansion and comprising from 6 to 28% nickel, manganese in amounts ranging from 11 to 3% in accordance with the amount of nickel present and the remainder iron and minor impurities,

said alloy containing not'morethan .3% carhon and the amount. of nickel plus two and one-half times the manganese being not less than 30% nor more than 36% of the alloy.

' 4. An alloy havinga high reversible temperature coefiicientof expansion and comprising from 8 to 24% nickel, manganese in amounts ranging from 10 to 4% in accordance with the amount of nickel present and the remainder iron and minor impurities, said alloy containing not more than 3% carbon and the amount of nickel plus two and one-half times the manganese being not less than 30% nor more'than 36% of the alloy. I

5. An alloy having-a high'reversible temperature coefficient of expansion and comprising from 10 to 20% nickel, manganese in amounts ranging from 10 to 6% in accordance with the amount of nickel-present and the remainder iron and minor impurities, said alloy containing not more than .3%vcarbon andthe amount of nickel plus two and one-half times the manganese being not less than 30% nor more than 36% of the alloy.

6. An alloy having ahigh reversible tern-- perature coefficientof expansion and comprisingfrom 10 to 16% nickel, manganese in amounts ranging from 10 to 7% in accordance with the amount of nickel present and the remainder iron and minor impurities,

said alloy containing not more than .3% car 4 bon and the amount of nickel plus two and one-half times the manganese plus two and one-half times the manganese being not less than 30% nor more than 36% of the alloy.

7. An alloy having a high reversible temperature coeflicient of expansion and com- HOWARD soorr.

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